Researchers take engineered heart up a notch

A team of researchers from MIT, Harvard University and Boston Children’s Hospital has added electronic sensors to tiny, sponge-like scaffolds which can be implanted into patients or used in the lab to study tissue responses to potential drugs.

The scaffolds are used to control the three-dimensional shape of engineered tissue.

Sensors, made of silicon nanowires, could be used to monitor electrical activity in the tissue surrounding the scaffold, control drug release or screen drug candidates for their effects on the beating of heart tissue.

The research could also pave the way for development of tissue-engineered hearts, according to paper author Robert Langer, David H. Koch Institute Professor at MIT which was published online Aug. 26 in Nature Materials.

“It brings us one step closer to someday creating a tissue-engineered heart, and it shows how novel nanomaterials can play a role in this field,” said Langer.

The research team set out to design a 3-D scaffold that could monitor electrical activity, allowing them to see how cells inside the structure would respond to specific drugs. Cellular platforms that incorporate electronic sensors consisted of flat layers of cells grown on planar metal electrodes or transistors do not accurately replicate natural tissue in 2-D.

The new scaffold is built out of epoxy, a nontoxic material that can take on a porous, 3-D structure. Silicon nanowires embedded in the scaffold carry electrical signals to and from cells grown within the structure.

“The scaffold is not just a mechanical support for cells, it contains multiple sensors. We seed cells into the scaffold and eventually it becomes a 3-D engineered tissue,” said researcher Bozhi Tian.

Electronic sensors made of silicon nanowires are small, stable, can be safely implanted into living tissue, and are more electrically sensitive than metal electrodes. The nanowires, which range in diameter from 30 to 80 nm, can detect voltages at the level of electricity that might be seen in a cell.

Using the engineered cardiac tissue, the researchers were able to monitor cells’ response to noradrenalin, a stimulant that typically increases heart rate.

The team also grew blood vessels with embedded electronic sensors and showed they could be used to measure pH changes within and outside the vessels. Such implantable devices could allow doctors to monitor inflammation or other biochemical events in patients who receive the implants. Ultimately, the researchers would like to engineer tissues that can not only sense an electrical or chemical event, but also respond to it appropriately — for example, by releasing a drug.

“It could be a closed feedback loop, much as our autonomic nervous system is,” said Daniel Kohane, director of the Laboratory for Biomaterials and Drug Delivery at Children’s Hospital. “The nervous system senses changes in some part of the body and sends a message to the central nervous system, which then sends a message back to take corrective action.”

The team is now further studying the mechanical properties of the scaffolds and making plans to test them in animals.

The research was funded by the National Institutes of Health, the McKnight Foundation and Boston Children’s Hospital.